What’s the Difference Between “PYREX” and “pyrex”?

The two logos—PYREX (all caps) and pyrex (lowercase)—have different meanings today.

Historically, both logos were used for glassware made from borosilicate glass. But over time, ownership and manufacturing processes changed. Corning, the original maker of Pyrex, licensed out the brand. Now, the type of glass used often depends on where the product is sold.

“pyrex” (lowercase): Typically found on products sold in the United States, South America, and Asia. These are usually made from tempered soda-lime glass.

“PYREX” (uppercase): Still used in Europe, Africa, and the Middle East, where products are often made from borosilicate glass.

Which One Is More Likely to Shatter?

Originally, pyrex was made with borosilicate glass, making it very resistant to thermal shock. However, due to boron’s high cost and environmental concerns, many manufacturers switched to tempered soda-lime glass.

While tempered glass is more durable than untreated soda-lime, it does not handle sudden temperature changes as well as borosilicate. This is why some people have experienced dishes shattering after moving them from the fridge directly to a hot oven.

If your dish is labeled PYREX (all caps), it is likely made of borosilicate glass and is safer for drastic temperature changes.

If it’s labeled pyrex (lowercase), it is likely made of tempered soda-lime glass, so you should be more cautious when using it with high heat or sudden temperature shifts.

Final Thoughts

When it comes to kitchen safety, the difference between PYREX and pyrex really does matter. Always check the labeling on your glassware, especially if you frequently use it for baking or reheating. While both types of glass have their strengths, understanding what you’re working with helps you cook smarter—and safer.